Seatbelt interlocks have been used in the past in vehicles and can help ensure that occupants are properly belted before the vehicle can be started. Systems relying on just a switch inside a seatbelt buckle may be tricked by a seat occupant sitting on a buckled belt rather than placing the belt over their lap, and then buckling the belt. There is a need for a system that detects when a seatbelt is properly used by a seat occupant.